Field of the Invention
The present invention relates to a system and a method for controlling valve timing of a continuous variable valve duration engine. More particularly, the present invention relates to a system and a method for controlling valve timing of a continuous variable valve duration engine that simultaneously controls duration and timing of the continuous variable valve.
Description of Related Art
An internal combustion engine combusts mixed gas in which fuel and air are mixed at a predetermined ratio through a set ignition mode to generate power by using explosion pressure.
In this case, a cam shaft is driven by a timing belt connected with a crank shaft that converts linear motion of a cylinder by the explosion pressure into rotating motion to actuate an intake valve and an exhaust valve, and while the intake valve is opened, air is suctioned to a combustion chamber and while an exhaust valve is opened, gas which is combusted in the combustion chamber is exhausted.
In the operations of the intake valve and the exhaust valve, only when a valve lift and a valve opening/closing time (timing) are controlled according to a rotational speed of an engine, optimal engine performance can be secured. Therefore, a continuous variable valve duration (CVVD) device controlling an opening period of an intake valve and an exhaust valve of the engine and a continuous variable valve timing (CVVT) device controlling an opening and closing timing of the intake valve and the exhaust valve of the engine have been developed.
FIG. 3 is a diagram showing a situation in which a CVVD device and a CVVT device control an intake valve and an exhaust valve of the engine.
The CVVD device adjusts an opening period (duration) of the valve with fixing a time point of maximum opening (peak lift), and the CVVT device advances or delays an opening and closing timing of the valve. That is, if an opening timing of the valve is determined, the closing timing is automatically determined according to duration of the valve.
However, both the CVVD device and the CVVT device are used in the engine, duration and timing of the valve should be simultaneously controlled.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.